In deep hole oil wells it is necessary to install a packing assembly at a great depth to seal the space between the well casing and the inner tubing to prevent oil from entering the annular space between the two. Very high oil pressure, such as 20,000 PSI, may be experienced at such sealing locations. In addition, because of thermal expansion and contraction of the long strings of pipe, there may be significant relative axial movement between the casing and tubing at the location of the down hole packing assembly. Such axial movement may cause the packing assembly to move over inwardly projecting welding beads and rough surfaces in the casing and the packing assembly may be subject to dirt and other solid particles entrained in the oil being sealed.
Because of the high pressure and other severe conditions to which the down hole packing assemblies are subjected, it has heretofore been the common practice to use either stacked sets of V type (chevron) packing rings or sets of solid cross-section elastomeric packing rings for this service. These types of packing rings have high contact pressure with the walls of the pipes even when not subjected to high fluid pressure and are susceptible to rapid deterioration and possible dislodgement from their mounting grooves due to the severe conditions to which they are exposed.